Yellow mold is a fungus that normally grows in dark and damp places. Several species of this mold exist, with some belonging in genera that are toxic or widely known to destroy wood. It is usually obvious when a building has a yellow mold infestation because the mold's color is often bright and difficult to miss. The color of this type of mold does vary, however; for example, some can appear almost white, and many are at least tinged with white. Correctly identifying the mold as a certain species is difficult and best left to a professional who can test it in a lab.
One type of yellow mold is toxic and generally belongs to the Aspergillus genus, in which several hundred other species of mold are categorized. Some of these molds, including the toxic yellow variety, can be dangerous to both humans and animals. If yellowish mold is found in a building, it should be treated with caution, and should not be touched without gloves or breathed in. Rampant yellow mold with white fruit bodies growing from it is a sign that the affected area has been very damp for a long time. Ridding the building of this mold usually involves treating any leaks and drying up moisture, or else it is likely the mold will come back.
Another mold that appears yellow is the species Serpula lacrymans, which is widely known as the house-eating mold because it is a fungus frequently responsible for dry rot. This mold tends to be dark yellow, almost gold in color, with white spores growing from it when conditions are right. As with most molds, warmth and moisture are ideal for the growth of dry rot. This type of mold was first documented in the early 1700s and has since aided or caused the deterioration of a vast number of wood buildings. Wood furniture, whether indoors or out, is also vulnerable to developing mold and will eventually be destroyed if not treated.
Providing good ventilation, limiting moisture, and keeping surrounding areas clean can help prevent the growth of yellow mold. Mold cannot thrive without moisture, so ventilating an area well and taking care of leaks quickly is usually a good defensive strategy. Regular cleaning of the area can also prevent the growth of yellow mold, as well as kill invisible spores. Soap and warm water, diluted bleach, or certain commercial cleaning products are routinely used for these purposes.